This invention relates to a technique for semiconductor devices and more particularly, to a technique effective for application to semiconductor devices having power MISFET (metal insulator semiconductor field effect transistor).
Transistors for high-power purposes dealing with electric power of several watts (W) or over are called power transistor, and various types of structures have been studied.
Among them, power MISFET includes ones called a longitudinal type and a transverse type and are classified into a trench-type structure and a planar structure depending on the structure of a gate portion.
Such power MISFET has a multitude of (e.g. several tens of thousands of) MISFET's in fine pattern connected in parallel in order to obtain high power.
For instance, Japanese Unexamined Patent Publication No. Hei 7 (1995)-249770 discloses power MISFET of the trench gate type.